This thesis contributes to the research about physical effect colors and photonic crystals. Monodisperse submicron-sized core shell beads, consisting of a silica core and a polymer shell, were synthesized and crystallized as a dispersion or in the melt into colloidal crystalline layers or films wherein the silica cores build up a face-centered cubic lattice similar to the natural gemstone opal. These artificial opals appear colored because of the wavelength and angle dependent reflection of the incident light. The optical contrast between the cores and their surrounding matrix determines the brilliance of the color. The main part of this thesis is dedicated to opal films which were produced by shearing a melt, using a method recently developed at the German Institute for Polymers. This technique enables the fast, industrially practicable production of large area opal films from unique particles with a hard, crosslinked core and a meltable, film forming shell, whereby core and shell have to be strongly interconnected by grafting. The synthesis of appropriate high quality silica polymer core shell particles was worked out exactly: Monodisperse silica beads were synthesized in a multistep Stöber process and hydrophobized with organosilanes. Subsequently they were coated with one or two polymer shells by emulsion polymerization of acrylic or methacrylic monomers. In accordance with literature, mainly the methacryl oxypropyl trimethoxysilane was used as organosilane, because of its capability to copolymerize with acrylics. However, a comparative study proved that other silanes without any acrylic functionality but with similar hydrophobicity were suitable as well. The opal films from silica polymer hybrid particles showed surprisingly brilliant colors, despite the small optical contrast between the silica cores and the polymer matrix. The optical properties were thoroughly evaluated by UV/vis spectroscopy. The most appealing color play was observed from elastomeric opal films which changed their color by deformation. Hard opal films were also transformed into inverse opal films. The silica cores were etched out with hydrofluoric acid, leaving pores at the cores' lattice sites. This increased the optical contrast, boosting the color brilliance enormously. The pores could be shaped isolated or interconnected. In the latter case, the wavelength and the intensity of the opaline color could be switched by infiltration of the pores with liquids. A minor part of the thesis deals with double inverse opals, a novel variety of inorganic inverse opals. Silica polymer core shell particles were crystallized by drying into opaline layers, the voids of which were filled with titania. The removal of the polymer yielded pores, ordered in the face-centered cubic lattice of a titania inverse opal, but with one additional, mobile silica core inside each pore. These randomly oriented inclusions eliminated the strong colors of the inorganic inverse opals almost completely. But the infiltration with liquids, optically masking the silica particles, revealed the opaline colors. The observation of this unique switching behaviour triggered theoretical simulations which pointed out a potential of double inverse opals for the switching of a complete photonic band gap. At the end of the thesis, a first hint of a phononic band gap in silica polymer opal films is presented as an outlook.